From: Segher Boessenkool
Sent: 16 April 2024 11:38
On Tue, Apr 16, 2024 at 03:02:52PM +0530, Naresh Kamboju wrote:
In file included from arch/powerpc/include/asm/io.h:672: arch/powerpc/include/asm/io-defs.h:43:1: error: performing pointer arithmetic on a null pointer has undefined behavior [-Werror,-Wnull-pointer-arithmetic]
It is not UB, but just undefined: the program is meaningless.
It is not a null pointer but even a null pointer constant here. It matters in places, including here.
It would help if the warnings were more correct :-(
Isn't it only a problem because the NULL pointer isn't required to be the all-zero bit pattern?
So when do we get a warning from using memset() on a structure that contains pointers? Since it is equally buggy.
Has anyone ever seen a system where NULL wasn't 'all zeros'? I've used a system where the 'native' invalid pointer was 'all ones', but even there the C code used 'all zeros'.
David
- Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)